The sales of industrial robots that has been driven by the automotive industry, is now moving into tasks as diverse as cleaning sewers, detecting bombs, and performing intricate surgery. The number of units sold increased to 120,000 units in 2010, twice the number as the previous year, with automotive, metal and electronics industries driving the growth.
Prior approaches to calibrating robots use measuring devices that measure either the inaccuracies of the robot after the robot is built or devices which measure work piece positions relative to the robot position prior to off-line programs. Prior art systems involve expensive equipment and specialized users and take longer.                U.S. Patent Application Disclosure No. 20090157226 (de Smet) discloses a robot-cell calibration system for a robot and it's peripheral. The system includes an emitter attached to the robot or its peripheral and emits a laser beam and a receiver also mounted to the robot or its peripheral at a point to permit calibration and for receiving the laser beam and to permit calculations to determine the dimension between the emitter and the receiver.        U.S. Pat. No. 6,408,252 (de Smet) discloses a calibration system and displacement measurement device for calibrating a robot system. The system comprises a linear displacement measurement device in conjunction with a robot calibration system. The linear displacement measurement device comprises an elongated member, a drum, a shaft, a drum displacement mechanism and a drum rotation sensor. The drum is displaced axially upon the shaft as the drum rotates when the elongated member is moved. The drum rotation sensor provides accurate information regarding the distance the elongated member travels. The displacement measuring device is used in an iterative manner with the calibration system for the purpose of the calibration of a robotic device.        U.S. Pat. No. 6,321,137 (de Smet) discloses a method for calibration of a robot inspection system. The system is used for inspecting a work piece to maintain the accuracy of the robot during inspection of work pieces on a production basis. The system includes means for storing a mathematical model of the robot, means for measuring the position of a target, and then calibrating the robot based upon input from the mathematical model and the position of the target.        U.S. Pat. No. 6,044,308 (Huissoon) discloses a method for calibration of pose of a tool contact point (TCP) of a robot controlled tool with respect to a tool sensor means in which the robot controlled tool is attached at an end-point of the robot. A TCP sensor is located in a preselected second pose with respect to the reference fixture for sensing position of the tool contact point. The method includes positioning the tool sensor so that the reference fixture is in a field of view of the tool sensor and calculating a pose of the robot end point with respect to the robot frame of reference, calculating a pose of the reference fixture with respect to the tool sensor means from a sensed position of the four topographically defined features of the reference fixture, and calculating a position of the tool contact point with respect to the reference fixture from a sensed position of the tool contact point with respect to the TCP sensor means.        
The primary object of the robotic work object cell calibration method of the present invention is to increase the accuracy of the off-line program and decrease robot teaching time. Still another object of the robotic work object cell calibration method of the present invention is to provide a calibration method which is simpler, results in improved precision, involves a lower investment cost, and which entails lower operating costs than the prior art.
What is needed is a robotic work object cell calibration method for using different robot tools on a shop floor without having to perform a recalibration for each tool. What is needed is a robotic work object cell calibration method that requires no additional computers or software to determine the accuracy of the robot tool or location of peripheral equipment, which uses existing body-in-white procedures, personnel computers and software and ways of communicating information amongst the trades, and requires little or no retraining to deploy.